composite materials has also been performed using differential scanning calorimetry (DSC). Latent heats of fusion were determined for both fluoride salts and their composite materials. It is clear that the latent heats of the composite materials agree well with the calculated values if one assumes that the porous volume is full of PCM. No appreciable supercooling is observed. The experimental data and the effect of porosity, pore size and composition of the molten salts is presented in detail in Refs [5] and [6]. Composite Type Receiver A preliminary analysis has been performed to evaluate the feasibility of the composite materials for a space solar receiver. The thermodynamic properties of the SiC-LiF composite are listed in Table I. The density and the heat capacity of the composite materials are estimated on an additive basis. Thermal conductivity is estimated assuming that Lichtenecker's equation [7] applies. The latent heat of fusion used is from our measured data [6]. A conceptual design for the composite receiver for a CBC system is illustrated in Fig. 10. Two heat exchanger tubes are coupled with each segment of the sector-shaped composite material. He-Xe circulating gas flows inside the outer tube and returns to the inner tube. Concentrated incident sunlight is directly absorbed on the inner side surface of the composite segments. Preliminary calculations indicate using a composite receiver of SiC/LiF results in a specific mass of about 50 kg/kWe. This is a weight reduction of about 30% compared to using LiF/canister receivers (the present space station design). Moreover, by assuming a CBC cycle efficiency of 40% at 1500 K [8], the SiC/MgF2 composite receiver achieves a specific mass of less than 40 kg/kWe. It is noteworthy that the high effective thermal conductivity of the composite material improves the efficiency of the LTES as well. He-Xe Loop Test A space solar receiver for a CBC must be designed to provide a constant supply of energy to the helium-xenon working fluid during both insolation and eclipse periods. An experimental apparatus for preliminary cyclic tests of LTES components is under construction. One of the main objectives of the tests is to define operating character-
RkJQdWJsaXNoZXIy MTU5NjU0Mg==